The production of pellets, also referred to as granules, from fine material or compacted and/or molten material is already known. The production of pellets, or wood pellets from preferably chopped biomass, such as wood chips, sawdust, or the like, is also already sufficiently known and is propagated in the field of renewable energy sources as a pioneering technology for climate protection, in particular in Europe. Typically, chip material from the wood-processing industry is used as the raw material, however, freshly cut timber or types of wood which are not usable in the wood-processing industry or waste materials can also be used. Pollutant-free base material is preferably to be used for the market for wood pellets for supplying small furnace facilities in single-family or multifamily houses. Block power plants or special high-temperature furnace facilities for generating heat and/or obtaining electrical energy (combination power plants) can also cleanly combust pollutant-charged material (pellets made of particle hoard or medium-density fiberboard with or without a coating or lacquering) in small amounts, however.
The wood pellets are typically produced in so-called pelletizing presses, in which the material to be compressed is pressed through boreholes of a matrix by moving and/or actively rolling rollers, also referred to as pan grinder rollers. The material (biomass) is shaped by the boreholes and discharged as strands from the boreholes. Boreholes are understood as all openings which are preferably implemented as essentially cylindrical, and are arranged in a matrix to feedthrough and shape the material. The boreholes can also have larger intake areas (depressions) to improve the compression procedure and can be hardened or can have hardened sleeves in the boreholes. A differentiation is made between flat and ring matrices in the field of matrices. Rollers revolve externally or internally around on ring matrices for the compression, on flat matrices, the pan grinder rollers roll circularly (mill construction) or linearly reversing. The invention is preferably concerned with flat matrices of the latter construction, but can optionally also be used with ring matrices. The possibilities for preparing and scattering the biomass, or the post-processing (chopping of the strands, cooling, storage, transport) of the pellets do not have to be discussed in greater detail. Reference is made in this regard to the prior art.
Due to the warming of the climate, which has been acknowledged worldwide in the meantime, the industry has been forced to accelerate and cheapen the large-scale industrial production of wood pellets. However, in particular in large production facilities, which are partially to be assigned to specialized mechanical engineering or heavy mechanical engineering, large and heavy machine parts are used. In particular the bearings or other sensitive machine elements or control devices required for this purpose must be protected from fine dust which occurs during the production or already exists. The efforts of development are directed toward sealing off the pressing or scattering chamber of the material to be compressed or the biomass to the least possible extent. The problem in this case is the movable parts (matrices and/or rollers) in the pelletizing press, which execute a relative movement to one another inside the pressing chamber or the scattering chamber. A large-scale encapsulation of the pressing chamber or the scattering chamber is typically performed, which has the result that an excessively large area of the pelletizing press is contaminated, with corresponding effects on moving or operationally-relevant facility parts. Reference is made hereafter to the scattering chamber, which therefore describes the contaminated area inside the pelletizing press.